A conventional AC-DC converter provides short-circuiting of a power supply only once during a half cycle in synchronization with a zero-crossing of a power supply voltage, thereby suppressing a harmonic current flowing through a reactor for improving power factor (see, for example, Patent Document 1).
There is disclosed an apparatus in which the size of a reactor is reduced by short-circuiting a power supply more than once during a half cycle of a power supply since short-circuiting of a power supply only once during a half cycle results in an increase in the size of a reactor (see, for example, Patent Document 2).
In addition, there is disclosed an apparatus having a switch for switching between full-wave rectification and voltage doubler rectification and a switch for providing short-circuiting of a power supply, in which a harmonic current is suppressed by switching using these two switches, thereby improving power factor (see, for example, Patent Documents 3, 4).
Further, there is disclosed an apparatus in which an input current is controlled by actuating a switch using high-frequency PWM so as to have a substantially sinusoidal waveform, thereby suppressing a harmonic current and improving power factor (see, for example, Patent Document 5).
Furthermore, there is published a paper on an attempt to suppress a harmonic current by two switching operations (see, for example, non-Patent Document 1).    [Patent Document 1] Japanese Patent No. 2763479    [Patent Document 2] Japanese Patent No. 3485047    [Patent Document 3] Japanese Unexamined Patent Application Publication No. 2003-9535    [Patent Document 4] Japanese Patent No. 3687641    [Patent Document 5] Japanese Patent No. 2140103    [Non-Patent Document 1] “A Switching Pattern Decision Scheme for Single-phase Multi-level Rectifiers” No. 1-61 Industry Application Division Meeting of the Institute of Electrical Engineers of Japan 2005